In August, LinkedIn allowed users to openly express interest in these types of opportunities on their profile page, but until Wednesday, these people could only be contacted for positions and couldn't actively search for them.

More than 600,000 people have expressed interest in these types of opportunities since August, said a LinkedIn spokesperson, and more than 3 million users have added volunteer experience and causes to their profile since 2011.

The social network will launch the marketplace with 500 postings on Wednesday, and plans to add more in the coming weeks. Organizations can post a volunteer opening or board seat the same way they would post a job. These new types of postings cost just 10% of what a job posting costs on LinkedIn, and the company plans to reinvest any revenues back into the program, says Meg Garlinghouse, head of LinkedIn Good.

The issue, however, with the new marketplace could be its visibility to users. The search page is not available in the site's navigation bar, and the only way users can visit the marketplace from LinkedIn.com is by clicking on volunteer opportunities that will appear in the "Jobs You May Be Interested In" tab along the right rail, Mashable says.

Users who receive emails highlighting "Job You May Be Interested In" will also receive volunteer openings. Otherwise, interested users will have to visit the marketplace directly by using the web addresses: volunteer.LinkedIn.com and nonprofit.LinkedIn.com.

Despite its separation of sorts from LinkedIn.com, Garlinghouse is adamant that volunteerism and professional networking can work together.

"Volunteering is not just good for the community, it's good for your career," she says. "Thats just another [reason] why we feel so bullish about making this a part of the LinkedIn experience."